The denomination rotary electric machines of the "in-out" type, designates those rotary electric machines having the stator located internally of the rotor.
Since the rotary assembly surrounds and screens the stator on all its cylindrical surface and on one of its two end faces, in-out machines are not provided with covers or shields as found in traditional, non-in-out machines which house the bearings and, being rgidly connected to the stator, support both the stator and rotor assembly.
In the "in-out" machines all the external walls, except one, rotate and it is therefore only on the side of the non-rotating wall that it is possible to provide a rigid component adapted to connect the machine with a static bearing assembly.
Further in the "in-out" machines the housings of the bearings, which cannot be placed in the shields (which do not exist), are normally realized by two segments of a tube or by a single through tube inserted into a central bore of the stator, such tubes having seats at different diameters adapted on the one hand for insertion into the bore of the stator and on the other for housing and registering the bearing seat and accessory components thereof.
The tube, prolonged beyond the non-rotating wall, is normally used as a rigid component adapted to render the machine rigid with an external body since it axially passes through all or part of the stator and therefore is rigid therewith, whereas its projecting part is subject to bending and is connected at its end to a flange which rigidly connects it to any external static bearing element.